Hi Justin, The purple discolouration which you refer to on the surfaces of the connector pins (photo labelled gold terms previous batch) may well be gold-tin intermetallic compounds. We have analysed something similar in the past. At the solder wetting front (edge of the solder as it wets over the pins), the ratio of gold to tin is very different from that at the "bulk" solder fillet. As a result, you can form a wide range of intermetallics with varying stochiometry (ratio of gold and tin atoms) which produce various different colours when viewed using light. The best way to confirm if you (or your supplier) need to is to get the parts examined using SEM+EDX (scanning electron microscope and energy dispersive x-ray analysis). If you are careful, you can also see these thin IMC layer when prepared in x-section - requires really good prep technique! Be happy to provide further background if you need it - get back to me if we can be of further help. Kind regards, Stewart Stewart McCracken MCS Ltd. Centre House Midlothian Innovation Centre Roslin Midlothian EH25 9RE m. +44(0)7711 541735 t. +44(0)131 440 9090 f. +44(0)131 440 9085 e. [log in to unmask] w. www.themcsgroup.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Justin Braime Sent: 08 October 2009 08:46 To: Administrator Subject: Re: [TN] gold connector discoloration Thanks for your input guys. The appearance of the connectors is fairly consistent across all the PCBs in the batch. So either there was some touching up done very consistently, or they've increased solder paste volume - the contractor uses the Mydata 'solder jet' technology rather than stencil printing. Apart from one pin on that one PCB, there's no solder on the gold mating surfaces, but the purple/black discoloration (it's not very clear on the photos compared to the actual view through the stereo microscope)on lower parts of the mating surfaces is widespread - not sure if this is flux wicking up the lead and causing the gold to tarnish, or even nickel passivation following gold dissolution? Either way, I've got misgivings about the reliability, so back the PCBs will go! Many thanks, Justin -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: 07 October 2009 18:14 To: [log in to unmask] Subject: Re: [TN] gold connector discoloration I agree with Victor on the solder-on-Au-connector issue... Looks to me that someone either reworked or touched-up the connectors after SMT or they hand soldered the connectors in... Adding flux to the connector and touching the SJs to clear a solder short or (most likely) to add solder to the joint will cause solder to wet up into the contact area on low profile connectors...Extra heat starts it but too much solder and flux does it every time... You'll have to ask the CM to remove and replace the connectors... Paul Paul Edwards Surface Art Engineering -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez Sent: Wednesday, October 07, 2009 10:06 AM To: [log in to unmask] Subject: Re: [TN] gold connector discoloration Beware of fretting with the solder on the gold plated contacts. Victor, -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gumpert, Ben Sent: Wednesday, October 07, 2009 9:34 AM To: [log in to unmask] Subject: Re: [TN] gold connector discoloration Justin, It looks like you have some solder that has made its way up the gold. The picture of the prior board looked as if there was less solder used to attach the connector, as there is still evidence of gold on the leads (where solder has not covered the leads as it has done in the 'new batch' image). Maybe they installed connectors that had been tinned, so there was additional solder in the process. Ben -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Justin Braime Sent: Wednesday, October 07, 2009 10:12 AM To: [log in to unmask] Subject: [TN] gold connector discoloration Hi Technetters, We've just received a new batch of boards from one of our subcontractors, and the Hirose DF12 header sockets have discoloration on the mating terminals. On previous batches, we have seen a little discoloration adjacent to the solder joints, but never up in the connector mating area itself. The process hasn't (allegedly) changed. I've posted some pics at: http://gallery.me.com/jbraime/100005 Any ideas as to the cause? Any detriment to functionality? Thanks in advance, Justin ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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